C0043 Brake Pedal Position Sensor Circuit "B" (Subfault)

C0043 Brake Pedal Position Sensor Circuit "B" (Subfault) is a diagnostic trouble code that indicates the vehicle's Brake Control Module, Anti-lock Braking System (ABS), Electronic Stability Control (ESC), Powertrain Control Module (PCM), or Body Control Module (BCM) has detected an abnormal condition in the Brake Pedal Position Sensor "B" circuit.

Many modern vehicles equipped with electronic brake boosters, brake-by-wire systems, or advanced driver assistance systems (ADAS) use multiple brake pedal position sensors for redundancy and safety. These sensors continuously monitor the brake pedal's position and movement, allowing the control modules to accurately determine the driver's braking demand.

When the control module detects that Brake Pedal Position Sensor "B" is providing an invalid, implausible, intermittent, or inconsistent signal, it stores the C0043 diagnostic trouble code and may disable several braking assistance and stability control functions.

This fault is commonly caused by a faulty brake pedal position sensor, wiring problems, connector corrosion, calibration issues, brake pedal mechanism faults, low system voltage, or control module failures.

What Does C0043 Brake Pedal Position Sensor Circuit "B" (Subfault) Mean?

Brake Pedal Position Sensor "B" continuously measures the exact position of the brake pedal.

The brake control module uses this information to determine:

• Brake pedal position

• Brake pedal travel

• Driver braking demand

• Brake assist requirements

The module continuously compares:

• Sensor A signal

• Sensor B signal

• Brake pressure

• Brake switch status

If Sensor "B" produces a signal that is:

• Missing

• Intermittent

• Outside the expected range

• Inconsistent with Sensor "A"

• Electrically implausible

the control module stores C0043.

Possible causes include:

• Faulty Brake Pedal Position Sensor "B"

• Wiring faults

• Connector problems

• Sensor calibration failure

• Brake pedal mechanism issues

• Control module malfunction

What Does the Brake Pedal Position Sensor Do?

The brake pedal position sensor measures exactly how far the brake pedal has moved.

The information is used by:

• ABS

• Electronic Stability Control (ESC)

• Traction Control System (TCS)

• Electronic Brake Booster

• Brake-by-Wire Systems

• Automatic Emergency Braking (AEB)

• Adaptive Cruise Control

• Transmission Shift Interlock

Many systems use dual sensors to verify braking input and improve reliability.

Why Is Brake Pedal Position Sensor "B" Important?

The brake pedal position sensor allows the vehicle to determine:

• Driver braking intent

• Brake pedal travel

• Brake application speed

• Brake assist requirements

Without accurate brake pedal information, several electronic safety systems may not operate correctly.

Symptoms of C0043

Symptoms vary depending on the vehicle and the severity of the fault.

Brake Warning Light

The brake warning light is commonly illuminated.

ABS Warning Light

The ABS warning light may also appear.

Stability Control Warning

Electronic Stability Control may become disabled.

Brake Assist Reduced

The brake assist system may not function correctly.

Cruise Control Disabled

Cruise control may fail to engage or may disengage unexpectedly.

Driver Assistance Systems Disabled

Depending on vehicle design, the following systems may also become unavailable:

• Automatic Emergency Braking

• Adaptive Cruise Control

• Collision Mitigation Braking

• Brake Assist

Brake System Warning Messages

Possible messages include:

• Brake System Fault

• Service Brake System

• Brake Assist Unavailable

No Noticeable Driving Symptoms

Some vehicles continue driving normally while only electronic safety systems remain disabled.

Common Causes of C0043

Several electrical and mechanical faults may trigger this code.

Faulty Brake Pedal Position Sensor "B"

The sensor may fail because of:

• Internal electronic failure

• Signal instability

• Physical damage

• Mechanical wear

Sensor Calibration Failure

Calibration may be lost after:

• Battery replacement

• Brake pedal repairs

• Brake booster replacement

• Sensor replacement

• Module programming

Damaged Wiring

Electrical circuit problems may include:

• Broken wires

• Short circuits

• Heat damage

• Chafed insulation

Connector Problems

Electrical connectors may develop:

• Corrosion

• Loose terminals

• Water intrusion

• Bent connector pins

Brake Pedal Mechanism Problems

Mechanical issues may include:

• Pedal binding

• Excessive play

• Damaged linkage

• Improper adjustment

Low Battery Voltage

Electronic brake systems require stable electrical voltage.

Possible causes include:

• Weak battery

• Charging system faults

• Poor ground connections

Control Module Problems

Although less common, the following modules may require service:

• ABS module

• ESC module

• Brake Control Module

• PCM

How Is C0043 Diagnosed?

Proper diagnosis requires checking both the brake pedal assembly and the electronic control system.

Scan the Vehicle

A professional diagnostic scanner should retrieve:

• Brake system codes

• ABS codes

• ESC codes

• Live brake pedal sensor data

Related fault codes often provide additional diagnostic information.

Monitor Live Sensor Data

Technicians verify:

• Brake Pedal Position Sensor A

• Brake Pedal Position Sensor B

• Brake pedal travel

Both sensors should respond smoothly and consistently while the brake pedal is pressed.

Inspect Brake Pedal Position Sensor

The sensor should be checked for:

• Proper mounting

• Physical damage

• Smooth operation

Verify Calibration

Many manufacturers require brake pedal sensor calibration after repairs.

Inspect Wiring and Connectors

Electrical inspection should include:

• Circuit continuity

• Voltage supply

• Ground integrity

• Connector corrosion

Inspect Brake Pedal Assembly

The brake pedal should move smoothly without sticking or excessive free play.

How Is C0043 Fixed?

The repair depends on the actual cause.

Replace Brake Pedal Position Sensor "B"

If the sensor has failed internally, replacement is required.

Perform Sensor Calibration

Many repairs require:

• Brake pedal relearn

• Sensor calibration

• Zero-point calibration

using a professional diagnostic scan tool.

Repair Wiring Problems

Possible repairs include:

• Repair damaged wires

• Replace damaged wiring

• Restore insulation

Repair Connector Problems

Repairs may include:

• Cleaning corrosion

• Repairing terminals

• Replacing damaged connectors

Repair Brake Pedal Mechanism

Damaged or improperly adjusted brake pedal components should be repaired.

Repair Electrical Supply Problems

Battery and charging system faults should be corrected.

Update or Replace the Control Module

If necessary, technicians may:

• Update module software

• Reprogram the module

• Replace the brake control module

After repairs:

1. Clear diagnostic trouble codes.

2. Perform sensor calibration if required.

3. Verify live brake pedal position data.

4. Road test the vehicle.

5. Confirm that C0043 does not return.

Can You Drive With C0043?

The vehicle usually remains drivable, but several important electronic braking and safety systems may not operate correctly.

Possible consequences include:

• ABS disabled

• Stability control disabled

• Reduced brake assist

• Cruise control unavailable

• Automatic emergency braking disabled

Repairs should be completed as soon as possible.

Is C0043 a Serious Code?

C0043 is generally considered a moderate to serious brake system fault.

Although normal hydraulic braking typically remains functional, inaccurate brake pedal position information can reduce the effectiveness of brake assist, ABS, stability control, and advanced driver assistance systems.

Prompt diagnosis and repair are recommended.

How to Prevent C0043

Regular maintenance helps reduce the likelihood of brake pedal position sensor faults.

Inspect Brake Pedal Components

Regularly inspect:

• Brake pedal mechanism

• Brake pedal sensors

• Mounting hardware

Maintain Battery and Charging System

Stable electrical voltage supports reliable sensor operation.

Inspect Wiring

Regularly inspect:

• Wiring harnesses

• Connectors

• Ground connections

Perform Calibration After Repairs

Always perform manufacturer-recommended calibration procedures after replacing brake pedal or brake booster components.

Address Warning Lights Promptly

Investigate brake system warning lights before additional faults develop.

Final Thoughts

C0043 Brake Pedal Position Sensor Circuit "B" (Subfault) indicates that the brake control module has detected an abnormal condition involving Brake Pedal Position Sensor "B".

The most common causes include:

• Faulty Brake Pedal Position Sensor "B"

• Calibration loss

• Damaged wiring

• Connector corrosion

• Brake pedal mechanism faults

• Low battery voltage

• Brake control module failures

A complete inspection of the brake pedal position sensor, brake pedal assembly, wiring, connectors, calibration status, electrical system, and brake control module is necessary to restore proper braking assistance and ensure safe operation of the vehicle's electronic brake and stability control systems.